An Ocean of Doubt

The extended pause in global warming over the last decade and a half has caused the climate campaign to become increasingly frantic to search for an explanation that keeps the narrative alive. One possible explanation is that the missing heat is being absorbed in the ocean rather than the atmosphere, though why the climate models didn’t predict this with greater accuracy is a question the climate modelers need to explain. There are some data to back up the ocean warming hypothesis, but the skeptics say there aren’t enough data points and the data don’t go back far enough to validate the hypothesis, so keep your eyes on this one.

One of the major gaps in the ocean story concerns not merely temperature but the absorption of carbon dioxide in the ocean, especially by plankton. And plankton growth is heavily influenced by the amount of iron in the ocean, which is why there has been a lot of theorizing, and a couple of experiments, about whether seeding the ocean with iron would increase CO2 absorption, with the calcified carbon sinking more or less harmlessly to the bottom of the ocean. We do know from paleoclimatology that the role of iron levels in the ocean played a role in ancient ice ages.

It turns out that another of our major gaps in oceanography is our grasp of what might be called the “iron cycle,” i.e., how much iron is fluxing into the ocean. A new study by the National Oceanographic Centre in the UK finds enormous variability in iron in the ocean whose impact is not adequately captured in climate models. From the Climate News Network summary:

LONDON – British scientists say estimates of the amount of iron dissolving into seawater around some of the world’s coasts may be drastically wrong.

They say there is no standard, one-size-fits-all way to measure how much iron enters the water in different parts of the globe. Instead, they say, the amounts may vary by up to ten thousand times between one area and another, with profound implications for the impact of the iron on the oceanic carbon cycle.

This uncertainty, they say, has probably led to iron’s impact being both exaggerated and underplayed. It is compounded by another discovery: that the iron enters the water by two mechanisms, not the one thought so far to be solely responsible. . .

[Lead author Dr. Will Homoky said] “Therefore these findings could certainly have implications for global climate modeling – to what extent is yet to be determined.”

“Our study shows that the amount of iron coming off different margins might vary by up to ten thousand times. In some regions we are probably over-estimating – and in others under-estimating – the influence of sedimentary iron supply on the ocean’s carbon cycle.”

The study is highly topical now as debate continues over where the heat caused by greenhouse gas emissions is going. Some claim that climate change is at a virtual standstill, because atmospheric heating has slowed a little. Others say the heat is going into the oceans. Intriguingly, it remains unclear which group can claim the study supports it.